Some Composting Necessities...or Not....

Thermophilic types of bacteria are responsible for the spontaneous heating of compost and can cause the compost pile to burst into flame if the pile is allowed to overheat. This happens if your pile becomes too dry, which makes the moisture content of your compost pile important to maintain. Compost requires 50-60% moisture for the micro-organisms to thrive and function properly. As composted materials lose water, it may be necessary to add 200-300 gallons of water for each cubic yard of finished compost. The compost pile is a living, breathing mass and should be kept with a moisture content equivalent to a squeezed-out sponge. The amount of water you need to add depends on the rainfall in your area, the size of your pile and the characteristics of your pile, but the moisture requirement should be easily met if the pile receives adequate rainfall and you include human urine. Water also comes from moist organic materials, like food scraps. If moisture is a problem, just collect rainwater or water from your household drains. Outside of a composting bin, it is recommended that your pile be at least 3 feet high and 3 feet wide to maintain moisture and warmth. If the pile is too small, you may find that only the middle remains moist and warm.

Freezing, which happens often during cold northern winters, will help destroy some potential pathogens and will also cause the micro-organisms in your compost pile to stop working. You can continue to add to your pile through the winter and the micro-organisms will just wake up and start to work up a steam after the thaw. Thermophilic types of bacteria thrive above 45°C (113°F), with some found to have optimum temperatures ranging from 55°C (131°F) to 105°C (221°F). Temperatures above 82°C (179.6°F) in the compost pile effectively stops biological activity. Actinomycetes tend to be absent in compost above 70°C (158°F), with fungi being absent in compost above 60°C (140°F), although most fungi cannot grow in temperatures above 50°C (122°F).

Anaerobic bacteria will decompose your pile in a slower and cooler process which stinks. To avoid such odours and ensure thermophilic decomposition of your compost pile, you want to cultivate aerobic bacteria. Aerobic bacteria suffer from a lack of oxygen and if your pile is too moist, you will drown them, promoting the growth of anaerobic bacteria. Also, if your pile is too compacted, there won't be enough air trapped inside to keep the aerobic bacteria happy. To further avoid any unpleasant odours, just be sure to cover anything that smells bad with clean and organic material, such as sawdust, peat, leaves, weeds, straw, hay, or even junk mail.

One way to achieve aeration is to use a fan and have a vent on the bottom to suck air out. This is generally more useful to large-scale composting and is good for keeping the pile from becoming too warm. Another way is to poke holes in the compost, or to physically turn the compost. If you build the pile so that air spaces are trapped in the compost then you don't need to do any of these things. You can trap air in your compost by using bulky material, like hay, straw, or weeds.

A common belief is that one must turn their compost piles. This is supposed to add oxygen to the pile which is good for aerobic micro-organisms. It is also supposed to prevent your pile from becoming anaerobic and smelly. Turning the pile is also supposed to ensure that the entire pile gets subjected to the pathogen-killing high internal heat. Turning the compost is supposed to make it look better for marketing purposes as it becomes chopped and mixed rather than coarse. Another reason why one might want to turn their compost pile is to speed up the composting process. The last two reasons really only matter if you are composting for marketability. Turning the pile actually dilutes the thermophilic top layer of the compost with the thermophilically spent layer that sinks lower and lower in the pile to be worked on by fungi, actinomycetes and earthworms, which can actually stop the thermophilic activity of your pile. If your pile is a continuous pile (that is, you are continuously adding new organic material), then, by turning the pile, you will be mixing the new material with the more composted material. If you turn your pile, it is suggested that you do batch composting, adding all your organic material at once.

Adding manure to your compost pile will help keep a good balance of nitrogen for all the carbon that comes from your organic garbage, which is necessary to keep your pile nice and hot. Most educators will tell you that old manure filled with straw or hay is good to add to your compost pile, but that you should never add human manure or the manure of cats and dogs due to the pathogens. Proper thermophilic composting, however, will readily destroy these as the temperatures are easily raised above that of the human body. "Hmmm. WHERE can a large animal like a human being find manure? Gee, that's a tough one. Let's think real hard about that one. Perhaps with a little "ingenuity and a thorough search" we can come up with a source. Where IS that mirror, anyway? Might be a clue there." (Humanure Handbook: Chapter 3: Four Necessities for Good Compost) A good carbon/nitrogen ration is 20-35 parts carbon to 1 part nitrogen. If there is too much nitrogen, it will not be used by the micro-organisms digesting your compost pile and will be lost in the form of ammonia gas.

Some believe that you need to add lime to your compost pile, or other mineral additives. Lime is used to kill micro-organisms in sewage sludge, which you do not need to do in your compost pile. Bacteria do not digest lime and aged compost is not acidic, no matter how acidic the organic garbage added to the pile may have been. Your garden soil might want lime, but the micro-organisms in your compost pile don't want it and you shouldn't give them what they don't want. The addition of lime to neutralize acidity is rarely necessary in aerobic decomposition and may do more harm than good due to the loss of nitrogen in ammonia gas. Don't assume that you need to add lime to your compost. The pH of your finished compost should be slightly higher than 7. If the measured pH of your finished compost is consistently acidic, then you may want to add lime to your pile.

Another misconception is that one should never put certain materials in their compost pile. This list includes: meat, fish, butter, bones, animal carcasses, cheese, lard, mayonnaise, milk, oils, peanut butter, salad dressing, sour cream, weeds with seeds, diseased plants, citrus peels, rhubarb leaves, crab grass, pet manures and human manure. The list probably includes any other food dishes that included the above materials. But when a compost pile heats up, all these organic materials are quickly degraded. The materials listed above require thermophilic composting conditions to achieve the best results. A thermophilic environment should prevail if those ingredients are included with all the other composting materials you will likely throw in it, just maintain a good nitrogen balance and good moisture, which should mostly be taken care of with manure and urine.

Newspapers and junk mail can be added to your compost pile, though the glossy pages retard composting and should be kept to a minimum. Newspaper inks still come from ingredients that can be harmful to human health if accumulated, although quite a few newspapers are turning to soy-based inks instead. Old phone books can be readily added to your pile, though you may want shred the pages and remove the glossy cover for the reasons stated above with newspapers and junk mail. Sanitary napkins and disposable diapers can be composted as well, although should be avoided unless you don't mind sitting there and picking plastic strips out of your finished compost. Toilet paper and the cardboard tubes in their center can be composted rather well. Bones are one of the things that still do not compost very well, but they will do no harm in a compost pile. Toxic chemicals, however, should always be kept out of your backyard compost pile, including pressure treated lumber, or sawdust from the same. Eggshells and hair are two other things that do not compost well. Bones and eggshells can be put in a fire, or bones can be given to your cats or dogs. Hair can be left out for the birds who like to make nests out of it.

Comfrey leaves, young weeds, grass cuttings, chicken and pigeon manure will all rot quickly and work as activators in your compost to get it started, but these will just decay and smell on their own. A good mix of ingredients is needed for this and you will find the best results through experience. You can also add wood ash, cardboard, paper towels, paper bags, cardboard tubes and egg boxes. Your compost will have a "balanced diet" if you include such things as fruit and vegetable scraps, tea bags, coffee grounds, old flowers, bedding plants, old straw and hay, the remains of vegetable plants, young hedge clippings, soft prunings, perennial weeds, or the bedding from your gerbils, hamsters and rabbits.

It is suggested that you keep two compost bins handy, about 5 feet by 5 feet. It should take about a year to fill the first, and it can be left to age for a year while you start to fill the second bin. After an initial two years, you will have a large batch of good compost for your use. Keeping a third bin in between these two will help ensure that material doesn't accidentally get dumped in the wrong bin. This third bin can be used to store your organic cover material, etc.